Press having means to prevent skewing movement of the ram

ABSTRACT

A press wherein there is provided an arrangement of opposing cylinder-piston motors to prevent skewing of the press ram or plasten when it is moved in its work stroke by cylinder-piston work motors. The opposing motors comprise a single acting motor and a double acting motor, each connected to an end of the ram in opposing relation to the work motors. The single acting cylinder is serially connected to the rod end of the double acting motor. The opposing motors are connected to a pressure accumulator which provides the opposing counter-pressure to overcome skewing movements of the ram and also provides pressure fluid to the opposing motors to retract the ram. In another embodiment, the ram is provided with an extension which is perpendicular thereto. Pressurized cylinder-piston motors are arranged on opposing sides of the extension to maintain it in a position wherein the ram is parallel to the base bed of the press. Valve means are provided to control the rate of fluid flow to the work motors connected to the ram. The valve means are actuated by means located near the extension whereby skewing of the ram moves the extension to actuate the valves to control the rate of flow to the work motors in the sense to eliminate the skewing movement and to resolve the ram to its parallel position.

United States Patent [191 Gygli et al.

[ Oct. 30, 1973 1 PRESS HA ING MEANS To PREVENT SKEWING MOVEMENT or THE RAM,

[75] I Inventors: Walter Gygli, Oftringen; Eduard Hanni, Zofingen, both of Switzerland [73] Assignee: Hammerle AG Maschinenfabrik,

Zofingen, Switzerland 22 Filed: Jan/19, 1972 21 Appl. No.: 219,073

Primary Examiner-Harvey C. Homsby Assistant ExaminerArthur 0. Henderson Att0rneyAbraham A. Saffitz [57] ABSTRACT A press wherein there is provided an arrangement of opposing cylinder-piston motors to prevent skewing of the press ram or plaste n when it is moved in its work stroke by cylinder-piston work motors. The opposing motors comprise a single acting motor and a double acting motor, each connected to an end of the ram in opposing relation to the work motors. The single acting cylinder is serially connected to the rod end of the double acting motor. The opposing motors are connected to a pressure accumulator which provides the opposing counter-pressure to overcome skewing movements of the ram and also provides pressure fluid to the opposing motors to retract the ram.

In another embodiment, the ram is provided with an extension which is perpendicular thereto. Pressurized cylinder-piston motorsare arranged on opposing sides of the extension to maintain it in a position wherein extension to actuate the valves to control the rate of flow to the work motors in the sense to eliminate the skewing movement and to resolve the ram to its parallel position.

3 Claims, 3 Drawing Figures PATENTEDUCT 30 I975 SHEET 1 BF 3 fig.1

PATENTEDnm 30 ms SHEET 30F 3 fig.3

PRESS HAVING MEANS TO PREVENT SKEWHNG MQVIEMENT OF THE RAM The present invention refers to a press having a ram or platen which is actuated at both ends by hydraulic or pneumatic working cyliners.

In the case of such presses, provision must be made to assure that with every distribution of load, including especially asymmetrical loading, the ram remains precisely parallel to the worktable, particularly during the downward movement of the ram and also during its return stroke. For the parallel control of the ram one can apply with good results a passage throttling control using a sleeve or other type valve with control ports in the form of slots or other passage means. In this system a device attached to the press for registering the skewed position of the ram displaces the sleeve valve in such a way'that the through cross-section of the one control slot increases, while that of the other control slot decreases. Thus one of the actuating pistons receives more pressure oil and the other less pressure oil, serving to restore the ram to the straight position. U. S. Pat. Nos. 3,120,799 and 3,199,539 illustrate the arrangements wherein such throttling controls are utilized. v

A disadvantage of this arrangement consists in the fact that the entire oil quantity must be passed through the narrow control passages. It is not possible to make the through cross-section of the control passages larger, since a precise control involving reactions to the smallest of skew positions would then no longer be assured.

In the development of the new press, the basic assumption was made that the total oil quantity for actuating the working cylinders should only be passed through the throttling control valve during the actual working stroke. During the rapid forward travel up to the start of the working stroke, and during the return stroke of the'ram, the throttling control valve should be put out of action. This produces the important advantage of a lower resistanceto flow and thus the faster actuation of the ram during the no-load strokes.

The object of the present invention is to propose a press for which these prerequisites are fulfilled, but for which in addition the ram is held in a position parallel to the worktable during the rapid forward travel and during the return stroke. According to the invention this is achieved through the fact that at least one conventional throttle control valve means with steplessly adjustable through cross-section is provided which is connectable to the individual working cylinders during the working stroke for altering individually the amount of pressure medium applied to them, and that at least two auxiliary pistons operating in hydraulic or pneumatic cylinders are provided which are arranged at a distance from each other in the area of and operatively connected to the ram in order to exert a counterpressure on the ram which is responsive to the forces occurring at the ram ends, and which counteract a skewed position of the ram during the rapid forward travel and during its return stroke. The same pistons may be used to effect a return of the ram.

The correction of a skewed position of the ram which may occur nevertheless, e.g., as a result of oil lost through leakage, can be accomplished by aligning the ram when it has reached a predetermined extreme position and at the same time bringing all of the counterpressures to the same value and-thereby equalizing the same. 7

According to an initial form of execution, one singleacting and one double-acting cylinder can be provided, whereby the cylinder space of the single-acting auxiliary cylinder is serially connected to the opposed cylinder space of the double-acting auxiliary cylinder. Preferably the other cylinder space of the double-acting auxiliary cylinder is connected to a hydraulic accumulator whereby a connecting line exists between the two cylinder spaces of the double-acting auxiliary cylinder in which an optionally closable valve can be fitted. In this form of execution of the press the valve is located in the area of the lower predetermined extreme position of the ram so that the ram can catuate it in the sense of opening when it reaches thisextreme position and equalize the pressure at both ends of the double cylinder.

In another form of execution of the press according to the invention, four auxiliary pistons can be provided which are supported in cylinders two of which are mounted on either side of a ram extension piece projecting downwards whereby each of the four piston rods which project perpendicular to the direction of movement of the ram and is provided on its end with a rotatable roller which can be brought to rest against the ram extension. In this form of execution two control valves are provided which are arranged one on either side of the extension, and are responsive to a skewing movement of the ram to control the flow of fluid to the several ram cylinders, and thereby synchronize the movement of the pistons connected to the ram. Furthermore, stops can be provided for the auxiliary pistons which only permit the rollers to be moved up to the point of contacting the extension.

Further objects and advantages-will be apparent by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a schematic view of the hydraulic circuit and the several components of the press;

' FIG. 2 is a schematic view showing the operative relationship of the cylinders to the ram or platen; and

FIG. 3 is a front view of a press illustrating another embodiment of the invention.

Referring to FIGS. 1 and 2, two actuating pistons l and 2 are connected to the ram or platen R with their piston rods 3 and 4 for rapid forward travel as well as for transmitting working pressure force to the ram. The working pressure for the press is generated in a highpressure pump 5 which is driven by a motor 6. A lowpressure pump 7 with high discharge rate, driven by the same motor, is provided for the rapid forward travel of the ram.

The pistons l and 2 are located in cylinders 8 and 9, which are connected to a throttling control valve means 14 by means of pipe 10 and 11 and check valves 12 and 13 therein. The control valve is connected to the high pressure pump 5 by a pipe 15 which contains a three-way reversing valve 16. Two branch pipes 17 and 18 having check valves. 19 and 20 therein connect pipe 10 and 11 to reversing valve 16 in sump tank 21.

Two further branch pipes 22 and 23 which likewise connect to the pipes 10 and 11 serve to carry the oil from the low pressure pump 7 via a pipe 26 nd via two check valves 24 and 25. A branch pipe 27 connects the pipe 26 with a bypass valve 28 from which the oil is led via a check valve 29 into the supply tank 21.

A pressure accumulator 33 is connected by means of a pipe 31 in which a check valve 32 is installed to a selector valve 30 which connects the pipe 31 optionally to the sump tank 21 or to the high-pressure pump 5. Provided for transmitting counterpressure or force to ram P and for retracting the same there is provided a single-acting piston 34 located in a cylinder 35 and a double-acting piston 36 mounted in a cylinder 37. The cylinder 37 is divided by piston 36 into opposing expansible spaces 37a and 37b. Cylinder space 37b is connected by a pipe 38 to the pressure accumulator 33. A pipe 39 serially connects cylinder space 35a of the single-acting cylinder 35. Finally, a connecting pipe 40 is provided which joins the two cylinder spaces 37a and 37b.

As schematically illustrated in FIG. 2, pistons 34 and 36 may be moved upwardly until they come in contact with ram R when it is in its upper extreme position. For disclosure purposes, FIG. 2 shows in dotted lines extensions connected to ram R which are positions with respect to pistons 34 and 36 to be contacted by them when actuated upwardly. It is obvious that pistons 34 and 36 may be arranged to contact ram R directly. At the extreme downward position of ram R valve means 41a and 41b are actuated by an adjustable actuating means 42 movable with ram R to position II for equalizing the pressures in cylinder spaces 35a, 37a and 37b and thereby restoring the relative positions of pistons 34 and 36 which may have been disturbed due to sealing leakage. Means 42 actuates the valve through its control member 43 connected to the valve members 41a and 41b.

The press just described operates as follows:

When the press is started up, the selector valve 30 is first switched to position II, thus connecting the highpressure pump via pipe 31 and check valve 32 to the pressure accumulator 33 which it charges. The valve members 41a and 41b are in position I, i.e., they shut off the pipe 40, so that the two pistons 34 and 36 are run to their uppermost extreme position to contact ram R directly or to operatively contact it by extension means connected thereto. Let us assume that the ram finds itself in its upper extreme position 'and should now be moved in rapid forward travel up to the workpiece being worked. This is accomplished by switching valve 30 to position I and closing the low-pressure bypass valve 28, the reversing valve 16 being in position 11. This connects the low-pressure pump 7 via pipe 26 to the cylinders 8 and 9 and the pistons l and 2 are driven downward by the large quantity of oil pumped. At the same time the cylinders 34 and 36 are driven downward in view of their contacting relation with ram R,

whereby in the cylinder space 35: a counterpressure is built up, which is diverted via pipe 39 into the cylinder space 37a of the cylinder 37 and from cylinder space 37b via pipe 38 into the pressure accumulator 33. Assuming that the working areas of pistons 34 and 36 are equal, the connection of the cylinder space 35 with the cylinder space 37a via pipe 39 produces a compulsory slaved movement of the pistons 34 and 36. This serves to support the ram and hold it in a parallel position. Should the ram now be non-uniformly loaded, such as by a heavy tool mounted on one-side, the piston on that side, for example, 34, will be move heavily loaded and tend to force its oil faster out of cylinder 35 than the valve 28 is opened, so that the low-pressure oil flows off via pipe 27 into the supply tank 21. The reversing valve 16 is still in position II, thus maintaining the connection of the high-pressure pump 5 via pipe 15 with the control valve means 14, which in turn transmits the pressure through the pipes 10 and 11 to the pistons 1 and 2. These move slowly downwards to do the work on the workpiece. Here the parallel control of the ram tends to take place by means of the control valve 14 which controls the proper flow of pressure'fluid to cylinders 7 and 8.

As soon as the ram has reached its bottom extreme position it actuates the valves 41a and 41b by means 42, 43 to their open position serving to equalize the pressures in the cylinder spaces 35a, 37a and 37b. In this way, one-sided oil leakage losses are equalized which, although causing only a negligibly small skewing of the ram during a single stroke would lead to an unbearable skewing of the ram after a large number of strokes.

For the return stroke of the ram, the valves 41a, 41b are reclosed and the reversing valve 16 switched to position I. This allows the pressure in the cylinders 8 and 9 to be let off through pipes 17 and 18 into the sump tank 21 as the ram moves upward under the influence of the highly compressed oil in the accumulator 33 acting on pistons 34 and 36. Now the parallel control is accomplished again by means of the pistons 34 and 36 in analogous fashion to that described for the rapid forward travel. After the upper extreme position has been reached, the entire procedure as described starts over again, in that the valves 16 and 28 are reversed in order to actuate the ram in rapid forward travel toward the workpiece.

A parallel guidance of the ram during the working stroke is achieved by the control valve 14, which controls the oil supply to the cylinders 8 and 9. But during the rapid forward travel under low-pressure pump 7 and the ram return stroke, the oil does not need to flow through the narrow cross-sections or passages of the control valve 14, thus making possible an increased speed in the ram movement. A cumulative skewed position of the ram caused by oil leakage losses is not possible, since the ram is restraightened after every working stroke in compulsory fashion by means of the actuation of valves 41a and 41b.

According to the execution example shown in FIG. 3, two columns 101 and 102 are supported in the frame 103 of the press; these columns house the working cylinders (not shown in detail which actuate the ram guide elements 104 and 105 which are carried by the columns. The ram 106 is joined to these guide elements 104 and 105 and carries on its underside an upper tool 107 which acts in conjunction with a lower tool 108 arranged on the frame 103 of the press. The guide elements 104 and 105 assume the guidance of the ram toward the front and the rear, while for its parallel guidance, a ram extension 109 is provided in the form of a massive steel plate which can, for example, be attached to the ram by means of bolts 110.

Four auxiliary cylinders Illa-111d are mounted on the frame 103 of the press. The two cylinders 111a and 1 11b are mounted on one side of the extension 109 and the two other cylinders l 11c and 111d are mounted on the other side of the extension 109, all in such a way that the piston rods 113 of the pistons 112 supported in them project all the way to the extension 109 in a direction perpendicular to the path of the movement of the ram 106.

Each of the piston rods 113 is provided with a fork 114 in which a roller 116 is supported so that it is free to rotate about an axle 115. The arrangement is made in such a way that, in the case of a displacement of the pistons 112 in the cylinders 111 in the direction of the extension 109, the rollers 116 come to rest against the extension 109 by piston 112 contacting an adjustable stop 112a. On either side of the extension 109 there is a control valve attached to the frame 103 of the press; the control rods 118 of these valves project perpendicularly to the direction of movement of the ram and their tips rest against the extension 109.

In the rest position of the press, the ram 106 is at the upper stop as shown in the drawing, so that a workpiece to be worked can be introduced between the tools 107 and 108. Now the control valves 117 are bypassed and the pistons 112 in the cylinders 111 are placed under pressure. This causes the pistons 112 to move against their stops 112a, with the result that the rollers 116 contact extension 109 of the ram 106, so that in the subsequent rapid forward travel of the ram 106 when the working cylinders are supplied directly by a lowpressure pump with a high discharge rate, extension 109 is guided by the rollers 116 and forced to remain in a position parallel to the frame. As soon as the upper tool 107 has struck the workpiece, the control valves are switched into the supply line of the working cylinders. Now the parallel position of the ram 106 is controlled by the individual regulation of the pressure 'medium supplied to the working cylinders, in that a deviation of the extension 109 caused by a skewing of the ram actuates one of the control rods 118 of the control valves 1 17, thus efl'ecting either a throttling of the leading cylinder or an acceleration of the lagging one. Since the working pressure of the main cylinders is substantially higher than that of the auxiliary cylinders, the rollers 116 resting against the extension 109 have no effect on the deviations of the extension 109 and therefore do not impair the functioning of the control valves 117 in any way. As soon as the working stroke is completed, the control valves 117 are bypassed once again so that there is nothing to prevent a rapid return stroke of the ram, whereby the parallel control of the ram is re-assumed by the rollers 116, which now, with the removal of the working pressure in the main cylinders, rest against the extension 109 once again. As soon as the ram has reached its upper extreme position the cycling begins anew. extreme position the cycling begins anew.

What we claim is: j

1. In a press, a ram, pressure working cylinder-piston motors connected to each end area of saidram to move it in a work stroke, said motors constituting working and opposing motors and comprising a first single acting cylinder operatively engaging one end area of the ram and a second double acting cylinder operatively engaging the opposing end area of said ram, to oppose the work stroke movement under the influence of the working motors, a pressure fluid supply line connected to each motor to supply working fluid thereto, throttle valve means in each of said lines to control the rate of flow therethrough, conduit means for serially connecting the cylinders of said opposing motors for transmitting an abnormal movement of pistons due to the skewing of the ram to the other opposing pistons, said conduit means including means for connecting said single acting cylinder to the piston rod end of said double acting cylinder and thereby compensating for the abnormal movement to restore the synchronous movement of the work motors for movement in the work stroke, a pressure accumulator connected to said opposing motors to pressurize said motors and to move their pistons into operative ram engaging position which cre ates a counter pressure force on the ram with respect to the working motor, a pipe line connecting both ends of the double acting cylinder, normally closed valve means in said pipe line to isolate said ends and means to open said valve means and thereby equalize the pressures in opposing motor cylinders.

2. In a press, a ram, pressure fluid working cylinderpiston motors connected to said ram to move it in a work stroke, a plurality of opposing cylinder-piston motors operatively connected to the ram to oppose its movement under the influence of the work motors, one of said plurality of motors being connected to each end area of the ram so that opposing motors comprise a single acting cylinder operatively engaging one end area of the ram and a second double acting cylinder operatively engaging an opposing area of the ram, a pressure fluid supply line connected to each motor to supply working fluid thereto,.throttle valve means in each of said lines to control the rate of flow therethrough, conduit means connecting said single acting cylinder to the piston rod end of said double acting cylinder which also serially connects said opposing motors for transmitting an abnormal movement of the pistons due to the skewing of the ram to the other opposing pistons to compensate such abnormal movement and thereby restore the synchronous movement of the work motors and a pressure accumulator connected to the opposing motors to pressurize said motors and to move their pistons into operative ram engaging position to create a counterpressure force on the ram with respect to the working motor.

3. A press as claimed in claim 2 wherein a pipe line is provided to connect both ends of the double acting cylinder, and there is further provided a normally closed valve means in said pipe line to isolate said ends, and means to open said valve means and thereby equalize the pressure in the opposing motor cylinders, said valve means including valve adjusting means responsive to ram movement and said valve actuating means opening said valve means at a predetermined stroke of theram.

* a: a: a 

1. In a press, a ram, pressure working cylinder-piston motors connected to each end area of said ram to move it in a work stroke, said motors constituting working and opposing motors and comprising a first single acting cylinder operatively engaging one end area of the ram and a second double acting cylinder operatively engaging the opposing end area of said ram, to oppose the work stroke movement under the influence of the working motors, a pressure fluid supply line connected to each motor to supply working fluid thereto, throttle valve means in each of said lines to control the rate of flow therethrough, conduit means for serially connecting the cylinders of said opposing motors for transmitting an abnormal movement of pistons due to the skewing of the ram to the other opposing pistons, said conduit means including means for connecting said single acting cylinder to the piston rod end of said double acting cylinder and thereby compensating for the abnormal movement to restore the synchronous movement of the work motors for movement in the work stroke, a pressure accumulator connected to said opposing motors to pressurize said motors and to move their pistons into operative ram engaging position which creates a counter pressure force on the ram with respect to the working motor, a pipe line connecting both ends of the double acting cylinder, normally closed valve means in said pipe line to isolate said ends and means to open said valve means and thereby equalize the pressures in opposing motor cylinders.
 2. In a press, a ram, pressure fluid working cylinder-piston motors connected to said ram to move it in a work stroke, a plurality of opposing cylinder-piston motors operatively connected to the ram to oppose its movement under the influence of the work motors, one of said plurality of motors being connected to each end area of the ram so that opposing motors comprise a single acting cylinder operatively engaging one end area of the ram and a second double acting cylinder operatively engaging an opposing area of the ram, a pressure fluid supply line connected to each motor to supply working fluid thereto, throttle valve means in each of said lines to control the rate of flow therethrough, conduit means connecting said single acting cylinder to the piston rod end of said double acting cylinder which also serially connects said opposing motors for transmitting an abnormal movement of the pistons due to the skewing of the ram to the other opposing pistons to compensate such abnormal movement and thereby restore the synchronous movement of the work motors and a pressure accumulator connected to the opposing motors to pressurize said motors and to move their pistons into operative ram engaging position to create a counterpressure force on the ram with respect to the working motor.
 3. A press as claimed in claim 2 wherein a pipe line is provided to connect both ends of the double acting cylinder, and there is further provided a normally closed valve means in said pipe line to isolate said ends, and means to open said valve means and thereby equalize the pressure in the opposing motor cylinders, said valve means including valve adjusting means responsive to ram movement and said valve actuating means opening said valve means at a predetermined stroke of the ram. 